Nanotech researchers report advances

PORTLAND, Ore.  Several nanotechology advances have been reported, including a nanoneedle invisibility cloak, the brightest nanoparticle and the highest temperature superconductor.

Purdue University researchers designed an optical cloaking device that surrounds objects to be made invisible with an array of nano-needles, each measuring 10 nanometers at the base and hundreds of nanometers long. The design capitalized on the cloaking device model proposed by researchers at the Imperial College in London and Duke University.

An invisibility cloak that can make a shaped object invisible must be made using a metamaterial, or a field of split-ring resonators that can bend waves away from their normal direction.

To achieve the cloaking effect of bending light around a hollow cavity, Purdue researchers designed an array of nanoneedles with a gradually changing refractive index from 0 (at their base) to 1 (at the needle's point). Simulations showed that the necessary bending occurred inside a cylinder to divert light around a cloaked object.

The next hurdle, beside building a model, will be making a multi-spectral cloak that can mask visible, radar, microwave and terahertz wavelengths. The current single-wavelength design, 632.8 nanometers (red), must be generalized with nanoneedles of varrying sizes or through architecture changes.
Meanwhile, Canadian and U.S. researchers researchers are claiming the world's brightest nanoparticle with fluorescence that is 170 times brighter than the previous record holder, quantum dots. Researchers at Clarkson University (Potsdam, N.Y.) and the National Research Council of Canada used a more conventional technology that entraps a large number of organic fluorescent molecules inside a nanoporous silicon-oxide matrix.

Advances have also been reported in carbon nanotube development. U.S. and Italian researchers achieved an temperature increase for high-temperature superconducting of as much as 10 percent.

In tests at Los Alamos National Laboratory and the Centro Atomico Bariloche-Instituto Balseiro, magnesium diboride was doped with double-walled carbon nanotubes resulting in a higher temperature for superconductivity. The Italian and U.S. labs worked together to enhance magnesium diboride's upper critical field and critical current density. They used Mg-vapor infiltration, which involves doping the superconducting material with double-walled carbon nanotubes.

Elsewhere, a kind of protein memorychip was demonstrated that uses protein to read, write and erase domains. Based on a new type of protein-nanolithography, teams from the Johann Wolfgang Goethe University and the Max Planck Institute for Biochemistry, created 50-nm features using an atomic force microscope. Sequences were shown to be movable and automatically assembled.

In oscillation mode, the microscope assembled protein sequences. Once written, they could be detached using the microscope's contact oscillation mode, then were selectively replaced with different protein sequences. The self-assembly process, the researchers claimed, permits quick writing, reading and erasing of protein arrays.